FI113962B - Heat-stable and chemical-resistant glass - Google Patents

Description

This invention relates to glass compositions which simultaneously exhibit a high temperature lower than 5 points of deformation, a low coefficient of expansion, and good chemical resistance.

The glasses according to the invention are interesting for all applications requiring such properties.

They are suitable, for example, for use in the glassware industry for the manufacture of pharmaceutical containers or bottles for pharmaceutical purposes.

The glasses according to the invention can also be formed into sheets which, when cut to the desired shape, possibly polished or treated, can act as elements in the manufacture of refractory glasses or substrates on which electrically active layers are applied. Such layer-coated substrates are generally referred to as "tiles" in the electronics industry. These substrates are combined into display devices, for example liquid crystal displays, plasma or electroluminescent displays.

Glasses known for their high physical stability at high altitudes; ' temperatures and good resistance to chemicals are many, and generally belong to a large group of borosilicate glasses, especially aluminum boron silicate glasses, such as •. ': 20 ka contains alkaline earth metal oxides.

Glasses which are converted into sheets and finally cut to form substrates are selected with particular regard to the physico-chemical properties required of them. Namely, when electrically active layers are applied to a glass substrate, several steps are required in which the glasses are exposed to relatively high temperatures. The glass must not deform during these steps, ie it must have the highest possible strain point temperature. In addition, the coefficient of thermal expansion of the substrate glass must be compatible with the layers applied to its surface. In addition, the glass must not contain virtually any material that could migrate into the formed layers and weaken their properties. Such substances are in particular alkalis.

2 113962

Also, the viscosity and devitrification properties of these glasses, i.e. the crystallization of the glass, must be suitable for the method chosen so that the resulting glass sheet is as even as possible with a smooth surface.

In addition, these glasses must be well resistant to chemicals in acidic environments, especially solutions based on hydrochloric acid.

One useful method is to introduce the molten glass into a device having the top of the downwardly tapering side walls serving as a drain. The glass flows along the side walls, and two currents are formed that combine at the tip of the device. The glass is then pulled vertically from top to bottom in the form of a flat sheet of glass. In such a process, the viscosity of the glass at a liquidus temperature must be at least 2 to 3 to 10 5. Such glasses are described, for example, in US-A-4 824 808.

In another method, molten glass is applied to a tin metal bath by the well-known floating glass method. Floatable glass compositions for use as substrates for flat display screens are described in particular in patent application WO 89/02877.

These glasses belong to the group of aluminum boron silicates and are rich in alkaline earth metal oxides. While these glasses have good physico-chemical properties for the intended application, a high percentage of their composition consists of expensive oxides such as B2O3, SrO and BaO. In addition, they are relatively viscous to the floating glass process when considered in the light of the examples illustrating the present invention. More specifically, the temperature • 'log η = 4 is 1150 ° C or higher, up to 1200 ° C. It will be recalled that the temperature of the same viscosity for ordinary float glass (quartz / sodium / calcium) is between 1000 and 1050 ° C.

25 Other glasses which may be formed by the method of floating glass are described in a patent application filed in France on 2 July 1991, under the number 91.08201.

These glasses are known in particular for having low viscosity at high temperatures (these glasses generally have a log η = 3.5 below 1180 ° C) and:. · Very low maximum devitrification rate. Thanks to this latter proprietary: · 30 femininity, crystallization does not occur during the formation of the glass, even if liquid. . the shower temperature may be 1230 ° C.

'·. The present invention relates to glass compositions which can be floated, which, by virtue of their physico-chemical properties, are suitable as refractory glasses or as substrates for active matrix displays, and which are further economically advantageous.

In particular, the invention relates to zinc oxide-free glass compositions which are applied to the surface of a tin bath at remarkably low temperatures; the liquidus temperature of these la-5 remains below the temperature corresponding to the characteristic viscosity log η = 3.5.

The invention also relates to glass compositions containing a limited amount of expensive ingredients.

A further object of the invention is to provide glass compositions which, in particular, provide containers that are resistant to temperature shock.

These objectives are achieved by the use of glass compositions consisting essentially of the following cationic percentages, within the stated limits:

SiO2 46-56% A1203 12-17% 15 B203 10-23%

CaO 9-15%

MgO 0.5-4%

SrO 2-7%; BaO 0-4% 20 Na 2 O + K 2 O <0.5%: TiO 2 0-3% * t ,; 'and has a viscosity curve such that the difference in viscosity is logr | = 4.5 and logr | = 2.5 * ti; 'between the respective temperatures <330 ° C, the resulting glass has a thermal expansion coefficient' * * 'of <50 · 10 7 / ° C, so that the viscosity logr | = 3.5 corresponding temperature is> 25 liquidus temperature, so its viscosity logr | = 4 corresponding to a maximum temperature of 1140 ° C and free of ZnO.

SiO2 is one of the oxides which forms the glass network of the glasses of the invention and * 'plays an essential role in their stability. With a cationic content of this component • · *: ... of less than 46%, the chemical resistance of the glass cannot be maintained beyond li-. , \ 30 adjusting B203, which is not desirable economically. When silicon-, · '; the amount of din is greater than 56%. The vitrified glass becomes more difficult to melt and the viscosity of the glass increases, cleaning and deposition on the tin bath becomes difficult.

4 113962 B203 is also essential for the stability of the glasses of the invention. This ingredient improves the chemical resistance of the glasses according to the invention, reduces their viscosity at high temperatures and the melting point of the vitrified mixture. B203 also reduces the risk of glass devitrification. When the amount of E ^ C ^ m is greater than 23%, its effect is reduced, and high concentrations of E ^ C ^ m also reduce the temperature below the deformation point. In less than 10%, the devitrification of the glass is enhanced and its viscosity increases.

Aluminum also contributes significantly to stability. This ingredient increases the temperature below the deformation point and, to some extent, the chemical resistance of the glass.

In less than 12%, durability remains too low, in more than 17%, glasses are more difficult to melt, and at high temperatures, their viscosity increases, and their chemical resistance is undesirably reduced.

In the glasses according to the invention, the oxides of alkaline earth metals also have a very important effect: they promote melting and decrease the viscosity at high temperatures.

Of these oxides, CaO has an important effect. In contrast to many components whose effect on the viscosity curve is practically reflected by the shift of the curve towards higher or lower temperatures, as the case may be, the effect of lime in the invention is the straightening of the viscosity curve. The two viscosities correspond to '; The difference in temperature is smaller for glasses of the invention than for ordinary quartz / sodium / calcium glasses.

As a result of this phenomenon, the temperature below the deformation point remains constant or even rises, the melting of the vitrified mixture and the cleaning of the resulting glass are facilitated, and the temperature at which the glass can be applied to the tin bath surface is lowered.

: 25 In order for the curve to be significant, the CaO content should be in the order of 9%. In more than 15%, CaO increases the expansion ratio in unacceptable ratios. SEA. A further advantage: the relatively high CaO-containing glasses of the invention are inexpensive because the raw materials of this ingredient are cheap. This economic benefit is the greater the more the glasses contain CaO and the less they contain E ^ C ^.

The glasses according to the invention systematically contain magnesium oxide, since this ingredient provides increased resistance to chemicals in the glass and reduces their expansion coefficient, and in addition reduces their viscosity at high temperatures.

5, 113962

The maximum MgO content is limited to 4%, since above this value this oxide increases the devitrification of the glasses according to the invention.

When SrO and possibly BaO are added, the viscosity of the glasses at high temperatures is reduced. These oxides also provide a reduced risk of devitrification.

In the glasses of the invention, SrO causes the viscosity curve to become straightened, but to a lesser extent than CaO. SrO can be added up to a certain concentration, about 7% cation, without too much expansion coefficient. BaO can be added to the glasses of the invention, but in relatively low concentrations. Although this oxide reduces the viscosity but does not affect the steepness of the viscosity curve, it increases the expansion coefficient quite significantly and the raw materials required are expensive.

The glasses of the invention may also contain limited amounts of other ingredients, such as TiO2, which increase the chemical resistance in particular.

In order to prevent the migration of substances into the substrate surface layer, the glasses according to the invention contain very little or no alkali metal oxides. The maximum alkaline content of these glasses is about 0.5% expressed as cationic percent.

Due to the combined action of the various ingredients described above, the compositions of the invention are easy to thaw and the resulting glasses have properties that perform •; 20 of them are particularly well suited for tin bath immersion.

! These benefits can be quantified by looking at the two specific viscosities; . 'Ten log η = 4.5 and log η = 2.5 measured temperature difference. In conventional quartz glass, the difference is greater than 330 ° C, in glasses according to the invention, the same difference is less than 330 ° C, in most preferred compositions less than 300 ° C.

.:. The compositions of the invention are relatively easy to thaw and the resulting glasses. **, easy to clean relative to glasses manufactured for the same purpose. This translates into reduced energy consumption and slower wear of the refractory parts of the furnace.

t I I

In the glasses of the invention, the temperature corresponding to a viscosity of log η = 4 is' ;; * '30 at about 1140 ° or less. This property is important because the pressure of the saturated vapor of the tin becomes significant from 1200 ° C and increases rapidly at higher temperatures.

6, 113962

Furthermore, the glasses according to the invention have a temperature corresponding to a viscosity of log η = 3.5 which is higher than their liquidity temperature. It helps to reduce the risk of devitrification during glass formation.

The glasses according to the invention have a temperature below the deformation point generally above 610 ° C, a coefficient of expansion less than 50 10 7 ° C / 7 ° C and are well resistant to corrosive hydrogen fluoride solutions.

The advantages of the present invention may be better understood by reference to the examples in the appended table.

Examples 1-8 illustrate glasses according to the invention, Example 9 is a counterexample showing the effect of CaO content on the difference in log η = 4.5 and log η = 2.5, respectively.

The thermal, devitrification and viscosity properties of the glasses representing the invention have been measured by methods well known to those skilled in the art. Their chemical resistance has been estimated by measuring the weight loss on both sides after standing in a polished 15x30x6 millimeter-15 r glass plate in acid solution. Loss is reported in mg / cm2. Hydrofluoric acid resistance (RHF) has been measured after 7 hours at room temperature in a solution of aqueous hydrofluoric acid and ammonium fluoride. This corrosive solution contains 50% hydrofluoric acid and 40% ammonium fluoride in a 1: 7 weight ratio.

The glasses according to the invention are obtained from vitrified raw materials, many of which are: ·, * natural products and must contain as little impurities as possible.

The most preferred compositions of the invention are particularly known for the following features alone or in combination:

SiO2 + A1203 <65% 25 10% <CaO <14%

SrO + BaO <4%

Na20 <0.2%

Float glass technology provides the glasses of the invention in the form of a precisely controlled thickness of tape.

30 Plates cut, possibly polished and treated to the desired shape are assembled into refractory glass or coated substrates for electronics.

7, 113962

The glass has a temperature lower than the deformation point of more than 600 ° C and an expansion factor of less than 5-10 ° C and is therefore suitable for the manufacture of refractory glass. As substrates, the glasses of the invention can be coated, in particular, with Si, SiOx, indium and tin oxide (ITO) and metal based layers to produce fine-film fine transistor networks.

They can also be coated with different layers to produce colored filters, for example, a Cr or NiCr film, which is then engraved by photolithography. Color coating (red, green, blue) is then performed with color application and light lithography. Finally, everything is covered with a polyimide layer and then an ITO-10 layer.

They may be coated with multiple layers, at least one of which is self-luminous by electric discharge.

The substrates thus obtained are combined into display devices, for example liquid crystal displays, plasma or electroluminescent displays.

Glasses according to the invention provide realized containers, for example glass bottles or nipple bottles, which, in use, require good heat shock resistance and high chemical inertia with respect to the products they will contain. These containers are made by known blow or meltblock-extrusion techniques.

20 Table

Example I Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9: SiO 2 48.30 46.98 46.66 46.99 49.43 47.36 47.85 46.84 52.35 A1203 13.85 16.00 16.22 16.24 15.95 16.09 15.89 16.52 16.09 25 CaO 10.04 9.89 11.33 9.97 13, 92 9.39 13.20 9.78 3.61 V: MgO 2.64 2.56 2.54 2.58 2.33 0.93 0.96 2.78 2.96

SrO 2.87 4.20 3.07 3.02 1.88 5.63 1.84 3.13 3.1

BaO 1.86 - - 0.98 - - - 1.71 5.05 ·: · B203 20.44 20.31 20.11 20.16 16.50 20.61 20.26 19.05 19.85 ' !!! Lower than 30 deformation points 627 636 630 632 642 637 635 625 616 *, ,, 'temperature (° C) •, expansion factor (10'7 / ° C) 49.5 48.2 47.6 48.0 48.1 49, 8 44.8 49.0 46.0 • E *: Liquid 1120 - 1090 - 1150 1060 1100 1100 1090. ··. Temp. logr | = 2 (° C) 1441 1436 1435 1452 1457 1466 1459 1448 1573 35 Temp. logn = 3.5 (° C) 1161 1170 1163 1174 1183 1183 1180 1175 1219 t Temp. 1θ £ η = 4 (° C) 1097 1110 1101 1112 1120 1117 1116 1111 1140 Temp. (k ^ = 2.5) - 286 286 278 277 282 292 286 282 359: ', - (ΐο§η = 4.5) (° C)' 'RHF (mg / cm 2) 13.25 9.24 8 , 45 16.22 11.34 7.88 8.89 8.36 10.07

Claims (9)

1. Heat stable and chemical resistant glass composition, which at the same time has a high temperature which is even lower is the temperature change temperature, a low expansion coefficient and a good chemical resistance, characterized in that it essentially consists of the following components, expressed as percent cations at the following interval: Si02 46-56% A1203 12-17% B203 10-23% CaO 9-15% MgO 0.5-4% SrO 2-7% BaO 0-4% Na 2 O + K 2 O <0.5% TiO 2 0-3% ,. that it has such a viscosity curve that the difference between the temperatures corresponding to the viscosity logr] = 4.5 and logi = 2.5 is <330 ° C, that the thermal expansion coefficient: v, the efficiency of the glass formed is 50 · 10 '/ ° C; the viscosity logi] = 3.5> liquidity temperature corresponds to its temperature corresponding to the viscosity logi] = 4 is at most 1140 ° C and does not contain ZnO. 2. Glass composition according to claim 1, characterized in that the sum SiO2 +; ; A1203 is poured as much as or less than 65%. Glass composition according to any of the preceding claims, characterized in: that the CaO content is 10-14%. 1. '. Glass composition according to any one of the preceding claims, characterized in that: *: by the sum of SrO + BaO being poured equal to or less than 4%. 113962 Glass composition according to any of the preceding claims, characterized in that the Na 2 O content is kept below 0.2%. Use of a glass composition according to any of the preceding claims for preparing a vessel by blowing or pressing a molten glass lump. Use of a glass composition according to any one of claims 1-5 for making a glass sheet by cutting a strip formed by disposing glass over a tin bath. Glass substrate, optionally coated with one or more electrically active layers, characterized in that it is made from a glass sheet defined in claim 7. 9. Refractory glass, characterized in that it contains at least one sheet of glass as defined in claim 7.% · · · · · · · · · · · · · · · · · · · ·